Lipid droplets (LDs) are dynamic organelles that are critical for cellular energy regulation. LDs consist of a neutral lipid core and a phospholipid monolayer, which allows for protein localization and binding. The mechanism of protein-lipid interactions at this monolayer remains less understood compared to those at biological membranes. These LD-associated proteins are essential to the development and functionality of LDs. One of the most abundant families of mammalian LD-binding proteins is the perilipin family, consisting of five proteins, named perilipin 1-5. Perilipins 1 and 2 are found bound to LDs, while perilipins 3-5 exchange between the surface of LDs and the cell cytosol. We are interested in the mechanism by which these exchangeable, or cytosolic, proteins bind to LDs. Here, we study the protein perilipin 3. Langmuir monolayer data from our lab suggest that the α-helix bundle located on the C-terminus of perilipin 3 has strong interactions with the lipid interfaces. To obtain a more comprehensive picture of the function of this C-terminal domain, we compare the full-length perilipin 3 to a truncated sequence that contains only this domain. Pendant drop tensiometry is used to examine protein binding to simulated LD monolayers with lipids that have the same headgroup structure but varying acyl chain saturation, and with lipids with the same acyl chain saturation but varying headgroup size and charge.
Lipid droplets (LDs) are dynamic organelles that are critical for cellular energy regulation. LDs consist of a neutral lipid core and a phospholipid monolayer, which allows for protein localization and binding. In order to better understand protein-lipid interactions at the LD monolayer, we focus on LD binding proteins in the perilipin family. Perilipin 3, a member of this family, contains a conserved bundle of amphipathic α-helices located at its C-terminus. Previous data from our lab suggest that this C-terminal α-helix bundle has strong interactions with lipid interfaces. Here, we use pendant drop tensiometry as a more physiologically relevant LD model to obtain a more comprehensive picture of the function of this C-terminal domain.